Smart cards are standardized portable articles defined in ISO standard 7816, and they can be used in particular to provide secure management of confidential data and to provide identification. In order to communicate with the outside world, these cards generally make use of the communications protocols defined in the third and fourth parts of the above-mentioned standard. In particular, these involve a protocol that is well known to the person skilled in the art under the reference T=0, which implements commands of a defined format: application protocol data unit (APDU) commands.
The universal serial bus (USB) standard describes a universal serial bus system and has been developed to make it possible for data interchanges between a host station, e.g. a workstation constituted by a personal computer, and any peripheral device, e.g. a printer or a keyboard, to be managed in a manner that is both simple and fast. The use of that system represents numerous advantages. Firstly, it requires two conducive lines VBUS and GND to power the peripheral device and two conductive lines D+ and D− for differential transmission of data signals. Secondly, it enables data to be transmitted at speeds that are generally higher than those proposed by the serial links conventionally installed on personal computers. These speeds are 12 megabits per second (Mb/s) at full speed and 1.5 Mb/s at low speed. Furthermore, it is compatible with hot “Plug & Play” of peripherals, i.e. it is compatible with the host computer recognizing such peripherals on a dynamic basis. By means of such recognition, the peripheral driver programs which reside in a mass memory of the host computer are loaded into a read/write memory of said computer only when said peripherals are connected. The same drivers are unloaded from said read/write memory when the peripherals are disconnected. In addition, the universal serial bus enables up to 126 peripherals to be connected in cascade on a single physical USB port. Finally, USB peripherals do not monopolize a hardware interrupt request (IRQ) managed by the components of the computer.
Nowadays, the need to make access to host stations secure and likewise access to servers associated with said stations is becoming increasingly important. The same applies to the need to make secure the transfer of data under the control of such stations, in particular from applications software in said stations dedicated specifically to email or to browsing the Internet, where it is desirable for data to be authenticated by means of encryption algorithms that make it possible to certify said data and to sign it.
Given the state of the art as set out above, the above-mentioned security needs have naturally been met by making use of smart cards that operate using the protocols set out in the third and fourth parts of ISO standard 7816, via special smart card readers that are connected to the USB ports of a host computer and that implement USB/ISO protocol conversion. Such readers communicate firstly with the host computer using the USB system and secondly with the card using the ISO system.
Unfortunately, such readers are very expensive. They need to have means for generating a clock for driving the operation of a central processor unit (CPU) in the microcontroller of the card via the clock (CLK) contact area of the card. They also need to have means for generating a reset signal and for transmitting said signal to the card via a specific contact area known as the reset (RST) area.
Furthermore, when the card is a pure ISO card, the procedures for communicating with the card do not have the above-mentioned advantages of the USB system relating in particular to a small number of conductive lines and to high data rates.